68 EXZYMEfy 



analogies to immune reactions (^loore"^"), and the proteolytic sub- 

 stances of the blood resemble the lysins in certain respects (Dick).'° 

 Enzj'uies and toxins also resemble one another in being readily ab- 

 sorbed by membranes, precipitates, and highly developed surfaces in 

 general.'^ Finally, there is much reason to believe that the hemo- 

 lytic toxin of cobra venom is a lipase, which acts by splitting lecithin 

 into hemolytic substances (Coca)."^* 



THE INTRACELLULAR ENZYMES "- 



Until a recent time our knowledge of enzymes in the animal body 

 was limited to those present in the digestive secretions. AVith few 

 exceptions these are without influence in pathological processes, since 

 they seem to be but little absorbed, and rarely enter the blood or 

 tissues in any other way. But with the more recently disclosed intra- 

 cellular enzymes, many of which are present in every cell,'^ the rela- 

 tion to pathology is very intimate. These intracellular enzymes, as 

 we now know them, and their chief properties, are as follows : 



OXIDIZING ENZYMES '* 



Although oxidation of organic compounds is the chief source of 

 energy in the animal body, yet the way in which it is accomplished 

 is very little understood. We only know that it is brought about 

 within the cells, and that substances that outside the body are oxidized 

 with difficulty, are completely oxidized to carbon dioxide and water 

 within the cells, and that this is done with just such a degree of rapid- 

 ity that the heat produced is in exactly the amount necessary for 

 the wants of the body. There can be little question that this oxida- 

 tion is accomplished through catalytic agents acting within the cells, 

 and certain of them have been placed in a condition permitting of 

 study. As yet their exact relations to intracellular oxidation are 

 not clearly defined, but for the present they may be grouped pro- 

 visionally as oxidizing enzymes. That some of them are highly specific 



«n TJiofhom. Jour., 1909 (4), 1G5. 



70 .Tour. Infectious Diseases, 1911 (9), 282. 



71 See Porter, Quart. Jour. Exp. Phvsiol., 1010 (3), ,375. 

 7ia,Jour. Infect. Dis.. 1915 (17). .351. 



72 See Vernon, Ergebnisse d. Physiol., 1910 (9), 13S; also liis monograph, 

 "Intracellular Knzvmes."' London, 1908. 



73irorlitzka (Arch. kal. hiol., 1907 (48). 119) and otlicrs have shown that 

 the difTcrent enz>ines ajipear one hy one in the d(>v('lo])nHMit of the ovum. Tlieir 

 activity is modified considerahly by infections (Sieher. Piocliem. Zeit.. 1911 (32). 

 108) and other diseases (Grossinaiin. (7)(V7.. 1912 (41). 181). 



74 f"om})lete 1)il)iio<rraphv and exliaustive discussion bv Kastle. liuli. Hvpienic 

 Lab., No. 59; by Loele, Eifrob. allfj. Path., 1912 (10, Pt.'2). 700: and by Rattelli 

 and Stern. Erpebnisse d. Pliysiol., 1912 (12). 90. Concerninsr the cliemistry of 

 vital oxidations see Dal<in. "Oxidations and Reductions in the Animal Body," 

 !Mono{rraplis on Piocliemistry. London. 1912. Good review l)y v. I'iirtli. "Chem- 

 istrv of Metabolism." Cliaps. 22 and 23; translated bv A. J. Smith. Pliiladclphia. 

 1910. 



